Electronic signal transmission and switching jack

ABSTRACT

The present invention relates to an electronic signal switching module with connectors on a first side for connecting with a variety of devices and sources and with jacks for receiving patch cords on a second side. The switching modules include two position switches in the circuitry connecting the jacks with the connectors which allow the module to be configured as a straight-through patching module, a fully normal module with paired jacks or a half normal module with paired jacks. One alternative of the invention utilizes card edge connectors on the first side. Another aspect of the invention involves a chassis for holding a plurality of switching modules adjacent to and electronically connected with a plurality of connecting modules. The switching modules may also include designation lenses adjacent to the jacks for holding indicia.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/474,730,filed Jun. 26, 2006, now U.S. Pat. No. 7,495,188; which is acontinuation of application Ser. No. 11/112,962, filed Apr. 22, 2005,now U.S. Pat. No. 7,092,176; which is a continuation of application Ser.No. 09/828,706, filed Apr. 6, 2001, now U.S. Pat. No. 6,992,257; whichapplications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to electronic signal transmission andswitching. More specifically, the present invention relates tomulti-function, multi-circuit switching jack modules for the audio,broadcast and entertainment industries.

BACKGROUND OF THE INVENTION

Analog and digital audio signals are transmitted over balanced andshielded twisted pair cables. These cables include a pair of insulatedconductors, either stranded or solid wire, which are surrounded by ametal foil shield. The shield serves to reduce the impact of externalelectromagnetic inference on the signal being transmitted over the cableand also to reduce the electromagnetic field generated by the signalsbeing transmitted over the cable.

In a professional audio and video industry application, a large numberof such cables will be in use to carry signals from sources toprocessing devices such as mixers or equalizers and further toamplifiers or other downstream devices. The environment in which thesesignals are generated is quite dynamic and requires the ability toquickly and easily shift connections between sources, and downstreamdevices. A jack field provides this sort of connection flexibility. Ajack field allows incoming signals to be patched into circuits connectedto devices and signals returning from devices to be patched intocircuits connected to downstream devices. Each jack in this jack fieldrequires three conducting paths, two for the balanced audio signal andone for the shield to serve as a grounding path. There are threeprincipal ways to connect these jacks to one another, depending on theneeds of the particular situation.

First, a jack field may be set up for non-normal connections, meaningthat each jack is connected directly to another jack. When a connectionbetween devices is needed, a patch cord must be used. For example, asource is connected to J1 and J1 is electronically linked to jack 1. Adevice is connected to J1 and J2 is electronically linked to jack 2. Tolink the source to the device, a patch cord would be used toelectronically link jack 1 to jack 2, as shown in FIG. 28 b. Without apatch cord in place in jack 1 or jack 2, no connection will exist foreither the source or the device, as shown in FIG. 28 a.

A second method of connecting jacks is referred to as normal. As anexample, a source and an device are designated to be linked togetherelectronically as a default or normal condition, but it is stillnecessary to be able to switch the source to another device, or connectanother source to the device, on occasion. To accomplish this, a sourceis connected to J1 and an device is connected to J2. J1 is alsoelectronically connected to J2. Jacks 1 and 2 are placed in the circuitconnecting J1 and J2, as shown in FIG. 29 a, and are configured suchthat, if a patch cord is inserted into jack 1 or jack 2, the connectionbetween J1 and J2 is broken, as shown in FIG. 29 b. If a patch cord isinserted into jack 1, it will not only break the J1-J2 connection, butthe patch cord will be electronically linked to the source connected toJ1. Similarly, a patch cord inserted into jack 2 will break the J1-J2connection and be electronically linked with the device connected to J2.So, in a normal configured jack field, two elements can be configured tobe normally electronically connected to one another but that normalconnection can be broken and the connections redirected as necessary.

A third method of connecting jacks is referred to as half-normal. In thedefault state, a source connected to J1 and an device connected to J2are connected together through jack 1 and jack 2, as shown in FIG. 30 a.This arrangement allows, for example, the feed coming from a source toJ1 to be monitored by a device connected into the normal circuit by apatch cord inserted into jack 1 without the insertion of the patch cordinto jack 2 causing the connection between the source and the deviceconnected to J2 to be broken, as shown in FIG. 30 b. In addition, theconnection between the source and the device can be broken by theinsertion of a patch cord in jack 2. When a patch cord is inserted intojack 2, the patch cord in jack 1 can then be used to patch the source toanother device and patch cord in jack 2 can be used to patch anothersource to the device, as shown in FIG. 30 c.

Another aspect of the connection between jacks and devices connected tothe jacks is the treatment of the shield. Typically, the shield of thecable connected to the first jack is electronically linked to the shieldof the cable connected to the second jack when the first jack and thesecond jack are electronically linked. It is desirable to have theability to link the shields either individually or jointly to a commonground. This allows maximum flexibility in the configuration in theelectronic linkages between the jacks, depending on the devicesconnected to the jacks.

While these connection schemes within a jack field are known, theability of users to reconfigure a jack field or a jack pair within ajack field from one to another of the three arrangements could beimproved. A variety of approaches have been used in the past, includingwire wrapping leads together between the jacks, soldering the leadstogether between the jacks, using straps or jumpers to reconfigureconnections between jacks, or using small metal plates of differentsizes and shapes to reconfigure the connection between jacks. In somedesigns, the entire jack field would need to be exchanged to reconfigurethe arrangement. This type of design does not allow the users toconfigure the circuits connected to individual devices and required alldevices connected to a particular jack field to be configuredidentically. Improvement to the ability to create and modify the stateof the connection between jacks and individual devices in the jackfields is desirable.

In addition, users of these types of devices and jack fields have verycomplex and dense wiring environments within their physical plants.Improvement to the density of connections possible in the limited spaceavailable within their physical plant without a loss of flexibility ofconfiguration is desirable.

SUMMARY OF THE INVENTION

The present invention relates to switching circuits such as for an audiosignal transmission environment. One aspect of the invention is aswitching module which contains pairs of audio jacks for receiving audioplugs and circuitry connecting these jacks to a second set ofconnectors. Included in the circuitry are two position switches whichallow the switching module to be configured for several differentswitching conditions.

A further aspect of the invention is a method of configuring theswitches to provide straight through, normal and half normal connectionsbetween the audio jacks and the second set of connectors.

A further aspect of the invention is a system including a chassis, withswitching modules and connecting modules, the connecting moduleselectronically linking audio cables connected to the connecting modulesto cables connected to audio plugs inserted into audio jacks of theswitching modules.

A variety of advantages of the invention will be set forth in part andthe description that follows, and in part will be apparent from thedescription, or may be learned by practicing the invention. It is to beunderstood that both the foregoing general description and the followingdetailed description are exemplary and explanatory only and are notrestrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate several aspects of the inventionand together with the description, serve to explain the principles ofthe invention. A brief description of the drawings is as follows:

FIG. 1 is a perspective view of the first side of an audio signaltransmission chassis with four switching modules mounted in the chassisand a fifth module in position for insertion into the chassis.

FIG. 2 is a perspective view of the second side of the chassis of FIG.1, showing three connecting modules mounted in the chassis.

FIG. 3 is a first perspective view of one of the switching modules ofFIG. 1.

FIG. 4 is second perspective view of the switching module of FIG. 3.

FIG. 5 is a side view of the switching module of FIG. 4

FIG. 6 is an end view of the switching module of FIG. 4.

FIG. 7 is an exploded view of the switching module of FIG. 4.

FIG. 8 is a circuit diagram of the switching module of FIG. 4.

FIG. 9 is a switching legend for the switching module of FIG. 4.

FIG. 10 is a first perspective view of one of the connecting modules ofFIG. 2.

FIG. 11 is a second perspective view of the connecting module of FIG.10.

FIG. 12 is a view of the cable connection side of the connecting moduleof FIG. 10.

FIG. 13 is a view of the switching module connecting side of theconnecting module of FIG. 10.

FIG. 14 is an end view of the switching module of FIG. 10.

FIG. 15 is a top view of the switching module of FIG. 10.

FIG. 16 is a first perspective view of a second connecting module ofFIG. 2.

FIG. 17 is a second perspective view of the connecting module of FIG.16.

FIG. 18 is a view of the cable connection side of the connecting moduleof FIG. 16.

FIG. 19 is a view of the switching module connecting side of theconnecting module of FIG. 16.

FIG. 20 is an end view of the switching module of FIG. 16.

FIG. 21 is a top view of the switching module of FIG. 16.

FIG. 22 is a first perspective view of a third connecting module of FIG.2.

FIG. 23 is a second perspective view of the connecting module of FIG.22.

FIG. 24 is a view of the cable connection side of the connecting moduleof FIG. 22.

FIG. 25 is a view of the switching module connecting side of theconnecting module of FIG. 22.

FIG. 26 is an end view of the switching module of FIG. 22.

FIG. 27 is a top view of the switching module of FIG. 22.

FIG. 28 a is a diagram of a prior art non normal circuit without a patchcord.

FIG. 28 b is a diagram of a prior art non normal circuit with a patchcord.

FIG. 29 a is a diagram of a prior art full normal circuit without apatch cord.

FIG. 29 b is a diagram of a prior art full normal circuit with a patchcord.

FIG. 30 a is a diagram of a prior art half normal circuit without apatch cord.

FIG. 30 b is a diagram of a prior art half normal circuit with a monitorconnected with a patch cord.

FIG. 30 c is a diagram of a prior art half normal circuit with a patchcord.

FIG. 31 is a front perspective view of an alternative designation lensfor holding indicia.

FIG. 32 is a rear perspective of the designation lens of FIG. 31.

FIG. 33 is a rear view of the designation lens of FIG. 31.

FIG. 34 is a top view of the designation lens of FIG. 31.

FIG. 35 is a rear view of the designation lens of FIG. 31.

FIG. 36 is a cross-sectional view of the designation lens of FIG. 31taken along AA in FIG. 35.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary aspects of the presentinvention that are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

Referring now to FIG. 1, an audio signal transmission chassis 10 isshown with four switching modules 100 mounted within the chassis and afifth switching module 100 in position to be inserted into chassis 10.Switching modules 100 are mounted by engaging card slots 12 in upperplate 14 and lower plate 16. Removable fasteners are then insertedthrough each module 100 and engaged by openings 18 in first upper plateflange 20 and first lower plate flange 22. The fasteners are not shownin FIG. 1 but may include any type of suitable removable fastener suchas a screw. Chassis 10 comprises upper plate 14 and lower plate 16 whichare joined to each other by end plates 24 and a series of intermediateplates 26. Mounting flanges 30 are included at the switching module endof sides 24. Mounting flanges 30 may be used to mount chassis 10 in aconvenient location, such as in an equipment rack. End plates 24 andintermediate plates 26 cooperate to form switch module bays 28. Each bay28 is configured to receive eight switching modules 100. Each bay 28includes eight card slots 12 in both upper plate 14 and lower plate 16and eight openings 18 in both upper plate flange 20 and lower plateflange 22 to allow the eight switching modules 100 to be mounted to thechassis. Projections 27 project transversely into slots 12 for centeringmodules 100.

Also mounted within each bay 28 of chassis 10 is a connecting module.Three different connecting modules 200, 300 and 400 are shown in FIG. 1.Different combinations of connecting modules 200, 300 and 400 can beused as desired. Further descriptions of switching module 100 andconnecting modules 200, 300 and 400 are included below. A similarchassis to chassis 10 of FIGS. 1 and 2 is shown and described in U.S.Pat. No. 6,186,798. Further connecting modules are also shown anddescribed in U.S. Pat. No. 6,186,798. Chassis 10 is also useable withthe jack access cards or modules shown and described in U.S. Pat. No.6,186,798. The disclosure of U.S. Pat. No. 6,186,798 is incorporated byreference. It is anticipated that module 100 can be adapted for use witha variety of standard and non-standard chassis and also in conjunctionwith other mounting systems.

Referring now to FIG. 2, a second perspective view of chassis 10 isshown. Connecting modules 200, 300 and 400 are mounted to chassis 10with fasteners inserted through the connecting modules and into openings18 in second upper plate flange 32 and second lower plate flange 34. Thefasteners are not shown in FIG. 2 but may include any type of suitableremovable fastener such as a screw.

Referring now to FIGS. 3 through 9, further details of switching modules100 are shown. FIGS. 3 through 6 show an assembled switching module 100.A card edge connector plate 102 is provided for connecting to one ofconnecting modules 200, 300 or 400. Card edge connector plate 102includes ten card edge contacts 104 on each side of plate 102, for atotal of twenty possible card edge connections. Connectors 118 are usedto electronically connect contacts 104 with circuitry on circuit board122. Standoffs 120 are used to physically connect plate 102 to jackhousing 124. Each of the ten posts 128 that are part of each connector118 extends through a hole 127 in plate 102 and is electronicallyconnected to a single contact 104. Each of the ten posts 128 that arepart of each connector 118 extends through a hole 129 in circuit board122 and is electronically connected to a circuit on board 122. Thesecircuits will be described in detail below but are not shown in FIGS. 3through 9 for clarity. Offsetting of card edge plate 102 allows module100 to be used in the arrangement described in U.S. Pat. No. 6,186,798.While modules 100 can be used in a variety of environments to supportaudio patching, the utility of these modules is enhanced by ensuringinterchangeability with an existing rack system such as described in the'798 patent.

A switch bank 114 with twelve switches 116 is mounted to circuit board122 with switch contacts 132 extending through holes 133. Each switch116 has two positions, open and closed. Switches 116 can be eithersliding or rocker switches or some other form of two position switchappropriate for mounting on a circuit board. Switches 116 may sometimesbe referred to as DIP switches. Switch contacts 132 are linked into thecircuitry on circuit board 122. The circuitry on circuit board 122 alsois electronically linked with spring contacts 134 which extend throughholes 135 in circuit board 122. The circuitry on circuit board 122 willbe described in detail below. Each of these spring contacts 134 is partof a spring 136 which is received in a slot 138 of jack housing 124. Theconfiguration and function of springs 136 will be described below in thedescription of the circuitry of module 100. Spring cover 130 enclosessprings 136 and slots 138.

On an opposite side of switching module 100 from card edge contacts 104are four audio jacks 106 positioned with access openings along face 140of jack housing 124 which are sized to receive bantam audio plugs (notshown). It is anticipated that other types of jacks and plugs may beutilized with module 100. A bantam audio plug for use with module 100has tip, ring and shield contacts which are attached to the tip, ringand shield conductors of a shielded audio cable. When a bantam audioplug is inserted into a jack 106, the tip, ring and shield contacts ofthe plug come into contact with selected springs 136 and thus to thecircuitry of switching module 100. At either end of face 140 aremounting extensions 112 through which are holes 111 for receivingfasteners 110. Fasteners 110 cooperate with openings 18 of chassis 10for mounting switching modules 100 to chassis 10. On face 140 adjacentto each jack 106 are designation devices 108. In the preferredembodiment, each designation device 108 is at least partiallytransparent to visible light and holds indicia of the circuit linked toan adjacent jack opening 106. Additional details of designation devices108 are provided below. Extending from jack housing 124 are tabs 126.Tabs 126 are sized and shaped to engage slots 12 in chassis 100 so thata module 100 can be slid into a bay 28 for mounting with fasteners 110into openings 18 in first upper plate flange 20 and first lower plateflange 22.

Referring now to FIG. 8, the wiring schematic of the circuitry of module100 and the configuration of springs 136 is shown. J1, J2, J3 and J4represent the jack openings 106 through face 140 of module 100. Withouta plug inserted into jack opening 106, a normal connection existsbetween the springs labeled R and RN and between the springs labeled Tand TN. When a bantam audio plug is inserted into one of the jackopenings 106, springs labeled T and R are displaced, breaking theconnection with springs TN and RN, respectively. When the plug is fullyinserted into jack opening 106, the tip, ring and shield contacts of theplug are electronically connected with the springs labeled T, R and S,respectively. Card edge connectors 104 are grouped into four groups, G1,G2, G3 and G4, each group including a tip connector, a ring connectorand a shield connector. Through the connection modules 200, 300 and 400described below, each group of three card edge connectors is connectedto a shielded cable leading to an audio source or other audio signaldevice. As shown in switching module 100, only thirteen card edgeconnections 104 are used, one for each T, R and S spring in jacks J1,J2, J3 and J4, and one to act as a common ground.

Referring now to FIGS. 8 and 9, the operation of switches 116 to changethe configuration of switching module 100 can be seen. Module 100 can beconfigured in three different conditions: no normal, half normal andfull normal. To configure module 100 to a no normal condition, allswitches 116 are left open. This condition has no normal stateconnections between any of G1, G2, G3 or G4. The only way a cable linkedto G1 connectors can be linked to a cable linked to G2 connectors isthrough the use of a patch cord with audio bantam plugs inserted into J1and J2. To configure module 100 to a full normal condition, switches 116labeled 1, 3, 7 and 9 are closed, with the remaining switches left open.This full normal condition allows a default electronic connectionbetween G1 and G2, and between G3 and G4, when no plugs are present inJ1, J2, J3 and J4. For example, assume G3 is linked to an audio sourceand this audio source is normally used in conjunction with a particularaudio effects device linked to G4. Without an audio plug in either J3 orJ4, this normal connection exists. When an alternative connection isrequired, patch cords can be inserted in J3 and J4 to disconnect thesource and the effects device from each other and patch them into othercircuits.

To configure module 100 to a half normal condition, switches 116 labeled2, 4, 8 and 9 are closed and the remaining switches are left open. Thiscondition also provides a default electronic connection between G1 andG2, and G3 and G4. In this half normal condition, an audio plug insertedinto J1 or J3 will permit another device or monitor to be linked intothe default circuit without breaking the circuit. If it is desirable tobreak the default circuit and patch the attached devices to alternativecircuits, inserting patch cords into J2 and J4 will serve to break thenormal circuits and allow patching to be carried out.

As shown in FIG. 8, the shield connectors of G1, G2, G3 and G4 areconnected directly to the springs labeled S in J1, J2, J3 and J4, whichwill in turn contact the shield contact of an audio plug inserted intothe jack. In some situations, it is desirable to have the shieldconnections also tied into a common ground or shield buss. Switches 116labeled 5, 6, 11 and 12 allow the shield circuit between G1 and J1, G2and J2, G3 and J3, and G4 and J4, respectively, to be tied into thecommon ground.

Referring now to FIGS. 10 through 27, connecting modules 200, 300 and400 will be described. The role of connecting modules 200, 300 and 400is to electronically link card edge contacts 104 to audio cables. Theseconnecting modules are flexible in terms of the connectors they providefor linking to these audio cables and the nature of the internalconnection between the card edge contacts and the rear connectors. Threealternatives each of cable connectors and internal connection areillustrated by modules 200, 300 and 400. All three of the modulealternatives include card edge slots for receiving card edge plates 102and electronically linking with card edge contacts 104. Additionalalternative versions of connecting modules are shown in theabove-referenced U.S. Pat. No. 6,186,798.

Referring now to FIGS. 10 through 15, module 200 includes insulationdisplacement connectors (IDCs) 214 for linking to individual conductorswithin audio cables and utilizes wire wrap tails 218 within the moduleto link the card edge connectors to the IDCs 214. Module 200 includes aC-shaped, open-ended housing 202, which also serves as the mountingsurface for card edge slots 220. Card edge slots 220 serve to interfacewith card edge plates 102 of modules 100 and include contacts whichelectronically link card edge contacts 104 with wire wrap tails 218. Inhousing 202 are mounting openings 206 and 210 for mounting module 200 tochassis 10 with fasteners inserted through openings 206 and 210 and intoopenings 18 in second upper plate flange 32 and second lower plateflange 34. Openings 206 include a larger lower opening 205 and a smallerupper opening 207 for passage of a fastener head and shaft,respectively. Openings 210 are configured as downward facing slots. Eventhough the ends of module 200 are open, access to the fasteners formounting or removal from a chassis 10 may be difficult, since multiplemodules 200, 300 and 400 may be mounted side-by-side, blocking the openends. Upper access slots 208 and lower access slots 212 allow users tosee and engage the fasteners, such as with a screwdriver, even whenadditional modules are mounted alongside module 200.

Mounted across the open end of housing 202 is plate 204. Plate 204serves as the mounting surface for IDCs 214, which are located in eightvertical columns corresponding to the eight card edge slots 220 mountedto housing 202. Each row of IDCs 214 includes twelve individualconnectors, for a total of 96 possible connections. Since audio cablesinclude three conductors each, tip, ring and shield, a total ofthirty-two cable connections are possible with module 200. Each IDC 214is linked through plate 204 to a connecting post 216 within housing 202.Links are made between wire wrap tails 218 and connecting posts 216 withindividual wires. Since a total of 96 wires linking posts 216 and wirewraps tails 218 are possible within housing 202, these wires have beenomitted from the FIGS. for clarity. Wire organizers 222 are providedbelow IDCs 214 for collecting and organizing the audio cables attachedto module 200. Also mounted on plate 204 are two separate grounds 224and 226. Ground 224 is a common chassis ground and ground 226 providesan isolated ground. Card edge contact 104 designated to be the commonground contact will be linked to one or the other of these two groundsby a wire from the corresponding wire wrap connector 218, depending onwiring requirements of a particular application.

Referring now to FIGS. 16 through 21, module 300 includes 3-pinconnectors 314 for linking to individual conductors within audio cablesand utilizes flex-circuit 318 within the module to link the card edgeconnectors to the 3-pin connectors 314. Module 300 includes a C-shaped,open-ended housing 302, which also serves as the mounting surface forcard edge slots 320. Card edge slots 320 serve to interface with cardedge plates 102 of modules 100 and include contacts which electronicallylink card edge contacts 104 with posts 322. In housing 302 are mountingopenings 306 and 310 for mounting module 300 to chassis 10 withfasteners inserted through openings 306 and 310 and into openings 18 insecond upper plate flange 32 and second lower plate flange 34. Openings306 include a larger lower opening 305 and a smaller upper opening 307for passage of a fastener head and shaft, respectively. Openings 310 areconfigured as downward facing slots. Even though the ends of module 300are open, access to the fasteners for mounting or removal from a chassis10 may be difficult, since multiple modules 200, 300 and 400 may bemounted side-by-side, blocking the open ends. Upper access slots 308 andlower access slots 312 allow users to see and engage the fasteners, suchas with a screwdriver, even when additional modules are mountedalongside module 300.

Mounted across the open end of housing 302 is plate 304. Plate 304serves as the mounting surface for 3-pin connectors 314, which arelocated in eight vertical columns corresponding to the eight card edgeslots 320 mounted to housing 302. Each row of 3-pin connectors 314includes 4 connectors, each with 3 connections, for a total of 96possible connections. Since audio cables include three conductors each,tip, ring and shield, a total of thirty-two cable connections arepossible with module 300. Each 3-pin connector 314 is linked throughplate 304 to a connecting post 316 within housing 302. Links are madebetween posts 322 and connecting posts 316 with flex circuit 318, whichis a printed circuit board created from flexible materials which enableit to be shaped as shown in the FIGS. Also mounted on plate 304 are twoseparate grounds 324 and 326. Ground 324 is a common chassis ground andground 326 provides an isolated ground. Card edge contact 104 designatedto be the common ground contact will be linked to one or the other ofthese two grounds by a circuit path on flex circuit 318 fromcorresponding post 322, depending on wiring requirements of a particularapplication.

Referring now to FIGS. 22 through 27, module 400 is a more compactconnection module utilizing board-to-board circuit connectors and 90-pinconnectors to link switching modules 100 to audio cables. Module 400includes housings 402 and 404. Housing 402 holds card edge slots 420 andhousing 404 holds 90-pin connectors 414. Card edge slots 420 serve tointerface with card edge plates 102 of modules 100 and include contactswhich electronically link card edge contacts 104 with board 422. One ormore board-to-board connectors 428 are mounted to board 422. 90-pinconnectors 414 are connected through housing 404 to boards 416. Boards416 include one or more board-to-board connectors 418, which mate withthe one or more board-to-board connectors 428 to electronically linkcard edge connectors 104 of switching modules 100 to audio cablesconnected to 90-pin connectors 414. In housings 402 and 404 are mountingopenings 406 and 410 for mounting module 400 to chassis 10 withfasteners inserted through openings 406 and 410 and into openings 18 insecond upper plate flange 32 and second lower plate flange 34. Eventhough the ends of module 400 are open, access to the fasteners formounting or removal from a chassis 10 may be difficult, since multiplemodules 200, 300 and 400 may be mounted side-by-side, blocking the openends. Upper access slots 408 and lower access slots 412 allow users tosee and engage the fasteners, such as with a screwdriver, even whenadditional modules are mounted alongside module 400. Openings 406 and410, and access openings 408 and 412 extend through both housings 402and 404. Openings 406 and 410 are configured as upwardly facing anddownwardly facing slots, respectively. A chassis ground 424 and anisolated ground 426 are provided in module 400 and depending on thewiring requirements of a particular application, card edge contacts 104linked to the common ground circuit on switching module 100 will belinked to one or the other of these grounds.

Designation device 108 is preferably a lens at least partiallytransparent to visible light so as to allow viewing of indicia heldbehind the lens, such as an indicia card. Referring now to FIGS. 31 to36, details of an alternative embodiment lens 508 of designation device108 for switching module 100 are shown. Lens 508 includes opposing sides520 and 522, opposing ends 524 and 526, and front face 512 and rear face514. Flats 516 are located at the rear of lens 508 and tabs 510 extendfrom flats 516 adjacent to sides 520 and 522. Lens 508 holds indicia onface 140 adjacent to jack 106. Like lens 108, lens 508 is mounted toface 140 by inserting tabs 510 into mounting slots 109 in face 140 ofswitching module 100. When mounted to face 140, flats 516 rest againstface 140. As shown in FIG. 36, line BB represents face 140. Line BBcooperates with rear face 514 and inner walls 528 to form an open endedindicia area 518, where indicia of the circuits connected to theadjacent jack 106, for example a paper strip, may be placed. Ends 530 ofarea 518 are open adjacent to opposing ends 524 and 526. These open ends530 allow indicia to be slid directly into area 518 when no modules aremounted in a chassis 10 adjacent to the module 100 to which lens 508 isattached. If an adjacent module interferes with direct access to openends 530, open ends 530 also provide an opening to insert a tool, suchas a thin flat screwdriver blade into to lever lens 508 from face 140.Designation lens 108, shown in FIGS. 3 through 9, has closed ends. Toinsert indicia into area 518 of a lens 108, a tool such as a thin probeor a wire end is inserted into opening 532 to lever lens 108 from face140.

The distance between opposing ends 524 and 526 is approximately equal tothe width of face 140, though slightly smaller so as not interfere withadjacent modules when mounted in chassis 10. As shown, this distance isapproximately 0.5 inches. Due to the small size of the lenses 508 andthus the limits on the size of the indicia held by the lenses, someelement of magnification by the lenses may be desired. This isaccomplished by using different radii of curvature for front face 512and rear face 514. As shown in FIG. 36, when viewed in cross section,rear face 514 is essentially planar while front face 512 is shaped alonga radius of curvature to provide magnification of indicia within area518 when viewed through front face 512. Rear face 514 could also beformed with a radius of curvature about the same origin as the radius ofcurvature of front face 512. The difference in curvature of front face512 and rear face 514 should be selected in conjunction with theproperties of the transparent material used to make the lens to achievethe desired level of magnification.

With regard to the foregoing description, it is to be understood thatchanges can be made in detail, especially in matters of the constructionmaterials employed and the shape, size and arrangement of the partswithout departing from the scope of the present invention. It isintended that the specification and the depicted aspects be consideredexemplary only, with a true scope and spirit of the invention beingindicated by the broad meaning of the following claims.

1. An electronic signal transmission module, comprising: a) a fronthaving a first group of connectors; b) a rear having a second group ofconnectors; c) a circuit board with board circuitry that electricallyconnects the first group of connectors with the second group ofconnectors; and d) switching circuitry that changes the board circuitrybetween a no normal configuration, a full normal configuration, and ahalf normal configuration.
 2. The module of claim 1, further including aswitch device having a plurality of switch positions that defines theswitching circuitry.
 3. The module of claim 2, wherein the switch deviceis located at a side of the module between the front and the rear of themodule.
 4. The module of claim 1, wherein the switching circuitry isdefined by a plurality of two-position switches mounted on the circuitboard.
 5. The module of claim 1, wherein the first group of connectorsincludes plug ports, the module further including tip, ring, and shieldcontact springs associated with the plug ports, the tip, ring, andshield contact springs being electronically linked to the boardcircuitry.
 6. The module of claim 5, further including designationlenses located on the front of the module adjacent to the plug ports. 7.The module of claim 5, further including ground sleeves that correspondto the contact springs, wherein the switching circuitry changes theboard circuitry between an independently-ground configuration and acommonly-ground configuration.
 8. The module of claim 1, wherein thesecond group of connectors is defined by rear card edge contacts.
 9. Themodule of claim 1, wherein the switching circuitry is defined by a bankof DIP switches, the bank of DIP switches being carried by the circuitboard.
 10. The module of claim 1, wherein the first group of connectorsincludes jacks, each jack including a spring assembly electronicallylinked to the board circuitry.